Merisant, largely owned by private-equity firm Pegasus Capital Advisors, is saddled with $560.7 million in debt, compared with $331.1 million in assets, according to U.S. Bankruptcy Court filings in Delaware. Its biggest creditors are holders of its publicly traded bonds, who are owed $362 million.

Merisant was scheduled to make $78.3 million in debt payments in the 12 months ending Sept. 30, according to a November filing with federal securities regulators. Some of those payments are due this month.

"It is fair to say the current turmoil in the credit markets made bank financing unavailable to Merisant to refinance its near-term maturities and interest payments," the company said in a statement to the Tribune.

Paul Block, Merisant's chief executive, said in a separate statement that "this is a financial restructuring of our balance sheet, not an operational restructuring of our business. We've already taken aggressive steps to cut costs."

No job cuts are expected because of the bankruptcy, he said. Merisant employs about 425 worldwide, including almost 70 in Chicago and 120 at a plant in Manteno, Ill., north of Kankakee.

Merisant has its roots in G.D. Searle & Co., the Skokie-based firm that invented the artificial sweetener aspartame in 1965. Monsanto bought Searle in 1985 and then in 2000 sold its aspartame-related businesses to separate buyers, with the tabletop sweetener operation christened Merisant.

Back then, Equal was the leading tabletop sweetener, with 37 percent of the market. Splenda, an artificial sweetener made by Johnson & Johnson has since come to dominate.

In 2008, Splenda grabbed 60 percent of the market, and Equal had only 11 percent, third after Sweet & Low.

The upshot: Merisant's revenues sank 18 percent from 2003 through 2007, when they totaled $290 million. For 2008's first nine months, sales were off another 6 percent from a year earlier.

Merisant is betting on future growth through PureVia, a zero-calorie natural sweetener derived from the leaves of the stevia shrub. Tabletop sweeteners under the PureVia brand are rolling out in stores nationwide.

Merisant also has partnered with PepsiCo , which plans on new beverages sweetened with PureVia. Block said the bankruptcy restructuring will free up more cash to support the expansion of PureVia.